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Re: Overhead anchors

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William

On various Corps projects that I have worked on adhesive anchors were
not allowed.  The argument was that 1) epoxy will allow creep such that
under long term tension loads the anchor will pull out, 2) keeping the
epoxy in the overhead hole during installation is difficult, and 3)
under elevated temperatures or fire conditions the epoxy will loose
strength and release the anchor creating an additional hazard.  Some of
the acrylic adhesives solve the temperature and creep problems but may
still have the installation problem.  Expansion anchors were accepted
for overhead conditions.

"Sherman, William" wrote:
> 
> Engineers in our office have expressed concerns with using expansion anchors
> in overhead applications, such as hanger supports, due to the potential of
> long-term slippage under constant tension. I do not see any cautions noted
> on the use of expansion anchors in such applications in manufacturer's
> literature or in ICBO reports. Does anyone know if there is documentation of
> slippage of "friction-type" anchors in constant tension applications?
> 
> We often prefer to use adhesive anchors in overhead applications, when
> drilled-in anchors are required - but concerns have also been raised with
> such anchors due to the potential softening of the adhesive in case of a
> fire. Also, overhead installation of adhesive anchors is more difficult.
> Does anyone have other recommendations for application of post-installed
> anchors in overhead applications?
> 
> William C. Sherman, PE
> CDM, Denver, CO
> Phone: 303-298-1311
> Fax: 303-293-8236
> email: shermanwc(--nospam--at)cdm.com
> 
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-- 
++++++++++++++++++++++++++
Forrest T. Braun, P.E.
BBFM Engineers, Inc.
Ph (907)274-2236
Fx (907)274-2520
Anchorage, Alaska
http://www.bbfm.com
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